Reduction Impairs the Antibacterial Activity but Benefits the LPS Neutralization Ability of Human Enteric Defensin 5.
Reduction Impairs the Antibacterial Activity but Benefits the LPS Neutralization Ability of Human Enteric Defensin 5.
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DOI：
10.1038/srep22875
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发表时间：
2016-03-10
影响因子：
4.6
通讯作者：
Wang J
中科院分区：
文献类型：
--
作者：
Wang C;Shen M;Zhang N;Wang S;Xu Y;Chen S;Chen F;Yang K;He T;Wang A;Su Y;Cheng T;Zhao J;Wang J
氧化型人防御素5（Oxidized human defensin 5，HD 5 OX）是潘氏细胞分泌的具有三个特征性二硫键的抗菌肽，可保护宿主免受小肠致病微生物的侵袭。硫氧还蛋白（Trx）可以在体外还原HD 5 OX，而还原的线性肽HD 5 RED的生化特性尚不清楚。在这里，我们首先确认HD 5 RED确实存在于体内。此外，我们发现，招聘的HD 5 RED革兰氏阴性菌的外膜和阴离子脂质A是低于HD 5 OX，和HD 5 RED是不太有效的穿透细菌的外膜和内膜，并诱导膜去极化，这赋予一个衰减的抗菌活性HD 5 RED。然而，由于其更高的结构灵活性，HD 5 RED与细菌脂多糖（LPS）的结合明显强于HD 5 OX。因此，HD 5 RED通过阻断LPS与LPS结合蛋白之间的相互作用，更有效地抑制LPS刺激的巨噬细胞中促炎细胞因子TNF-α的产生，从而表明HD 5 RED可能作为清除剂中和肠道中的LPS。这项研究提供了深入了解HD 5 RED的抗菌和免疫调节作用，并扩大了肠防御素的已知库。
Oxidized human defensin 5 (HD5OX), a Paneth cell-secreted antibacterial peptide with three characteristic disulfide bonds, protects the host from invasion by morbigenous microbes in the small intestine. HD5OX can be reduced by thioredoxin (Trx) in vitro, while the biochemical properties of the reduced linear peptide, HD5RED, remain unclear. Here, we first confirm that HD5RED does exist in vivo. Furthermore, we reveal that the recruitment of HD5RED to the outer membrane of Gram-negative bacteria and to the anionic lipid A is lower than that of HD5OX, and HD5RED is less efficient in penetrating bacterial outer and inner membranes and inducing membrane depolarization, which confers an attenuated antibacterial activity to HD5RED. However, due to its higher structural flexibility, the binding of HD5RED to bacterial lipopolysaccharide (LPS) is markedly stronger than that of HD5OX. Consequently, HD5RED is more effective in suppressing the production of the pro-inflammatory cytokine TNF-α in LPS-stimulated macrophages by blocking the interaction between LPS and LPS-binding protein, thus suggesting that HD5RED might act as a scavenger to neutralize LPS in the gut. This study provides insights into the antibacterial and immunoregulatory effects of HD5RED and expands the known repertoire of the enteric defensins.